{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "$id": "https://tightknit.com/schemas/slack-block-kit.schema.json",
  "title": "Slack Block Kit",
  "description": "JSON Schema (draft 2020-12) for Slack Block Kit payloads. Validates a top-level array of blocks. Individual block, element, and composition object schemas are exposed via $defs for re-use. Compiled from https://docs.slack.dev/reference/block-kit (fetched 2026-04-16). Surface restrictions (messages vs modals vs home) and payload-level rules (e.g. cumulative 12k char markdown limit, single-table-per-message, max two data-visualization blocks per message) are documented in $defs descriptions but not enforced at the per-block level.",
  "type": "array",
  "minItems": 1,
  "maxItems": 100,
  "items": { "$ref": "#/$defs/block" },

  "$defs": {
    "action_id": {
      "type": "string",
      "minLength": 1,
      "maxLength": 255,
      "description": "An identifier for the interactive element. Should be unique among all action_ids used in a single view/message."
    },

    "block_id": {
      "type": "string",
      "minLength": 1,
      "maxLength": 255,
      "description": "A unique identifier for a block. Should be unique within a single message or view."
    },

    "plain_text_object": {
      "type": "object",
      "additionalProperties": false,
      "required": ["type", "text"],
      "properties": {
        "type": { "const": "plain_text" },
        "text": { "type": "string", "minLength": 1, "maxLength": 3000 },
        "emoji": { "type": "boolean" }
      }
    },

    "mrkdwn_text_object": {
      "type": "object",
      "additionalProperties": false,
      "required": ["type", "text"],
      "properties": {
        "type": { "const": "mrkdwn" },
        "text": { "type": "string", "minLength": 1, "maxLength": 3000 },
        "verbatim": { "type": "boolean" }
      }
    },

    "text_object": {
      "description": "A text object — either plain_text or mrkdwn.",
      "oneOf": [{ "$ref": "#/$defs/plain_text_object" }, { "$ref": "#/$defs/mrkdwn_text_object" }]
    },

    "confirm_object": {
      "type": "object",
      "additionalProperties": false,
      "required": ["title", "text", "confirm", "deny"],
      "properties": {
        "title": {
          "allOf": [{ "$ref": "#/$defs/plain_text_object" }, { "properties": { "text": { "maxLength": 100 } } }]
        },
        "text": {
          "description": "Per Slack docs examples, this field accepts plain_text OR mrkdwn. Prose on the docs page says plain_text, but the example payload uses mrkdwn.",
          "allOf": [{ "$ref": "#/$defs/text_object" }, { "properties": { "text": { "maxLength": 300 } } }]
        },
        "confirm": {
          "allOf": [{ "$ref": "#/$defs/plain_text_object" }, { "properties": { "text": { "maxLength": 30 } } }]
        },
        "deny": {
          "allOf": [{ "$ref": "#/$defs/plain_text_object" }, { "properties": { "text": { "maxLength": 30 } } }]
        },
        "style": { "enum": ["primary", "danger"] }
      }
    },

    "option_object_plain_text": {
      "description": "Option object used in select / multi-select menus. text and description must be plain_text. url is not allowed here (overflow only).",
      "type": "object",
      "additionalProperties": false,
      "required": ["text", "value"],
      "properties": {
        "text": {
          "allOf": [{ "$ref": "#/$defs/plain_text_object" }, { "properties": { "text": { "maxLength": 75 } } }]
        },
        "value": { "type": "string", "minLength": 1, "maxLength": 150 },
        "description": {
          "allOf": [{ "$ref": "#/$defs/plain_text_object" }, { "properties": { "text": { "maxLength": 75 } } }]
        }
      }
    },

    "option_object_overflow": {
      "description": "Option object used in overflow menus. Adds optional url field.",
      "type": "object",
      "additionalProperties": false,
      "required": ["text", "value"],
      "properties": {
        "text": {
          "allOf": [{ "$ref": "#/$defs/plain_text_object" }, { "properties": { "text": { "maxLength": 75 } } }]
        },
        "value": { "type": "string", "minLength": 1, "maxLength": 150 },
        "description": {
          "allOf": [{ "$ref": "#/$defs/plain_text_object" }, { "properties": { "text": { "maxLength": 75 } } }]
        },
        "url": { "type": "string", "format": "uri", "maxLength": 3000 }
      }
    },

    "option_object_radio_or_checkbox": {
      "description": "Option object used in radio_buttons and checkboxes elements. text and description may be plain_text or mrkdwn.",
      "type": "object",
      "additionalProperties": false,
      "required": ["text", "value"],
      "properties": {
        "text": {
          "oneOf": [
            {
              "allOf": [{ "$ref": "#/$defs/plain_text_object" }, { "properties": { "text": { "maxLength": 75 } } }]
            },
            {
              "allOf": [{ "$ref": "#/$defs/mrkdwn_text_object" }, { "properties": { "text": { "maxLength": 75 } } }]
            }
          ]
        },
        "value": { "type": "string", "minLength": 1, "maxLength": 150 },
        "description": {
          "oneOf": [
            {
              "allOf": [{ "$ref": "#/$defs/plain_text_object" }, { "properties": { "text": { "maxLength": 75 } } }]
            },
            {
              "allOf": [{ "$ref": "#/$defs/mrkdwn_text_object" }, { "properties": { "text": { "maxLength": 75 } } }]
            }
          ]
        }
      }
    },

    "option_group_object": {
      "type": "object",
      "additionalProperties": false,
      "required": ["label", "options"],
      "properties": {
        "label": {
          "allOf": [{ "$ref": "#/$defs/plain_text_object" }, { "properties": { "text": { "maxLength": 75 } } }]
        },
        "options": {
          "type": "array",
          "minItems": 1,
          "maxItems": 100,
          "items": { "$ref": "#/$defs/option_object_plain_text" }
        }
      }
    },

    "slack_file_object": {
      "description": "Reference to a Slack file. Exactly one of url or id must be provided. Supported file types: png, jpg, jpeg, gif.",
      "type": "object",
      "additionalProperties": false,
      "properties": {
        "url": { "type": "string", "format": "uri" },
        "id": { "type": "string", "minLength": 1 }
      },
      "oneOf": [
        { "required": ["url"], "not": { "required": ["id"] } },
        { "required": ["id"], "not": { "required": ["url"] } }
      ]
    },

    "dispatch_action_config_object": {
      "type": "object",
      "additionalProperties": false,
      "required": ["trigger_actions_on"],
      "properties": {
        "trigger_actions_on": {
          "type": "array",
          "minItems": 1,
          "maxItems": 2,
          "uniqueItems": true,
          "items": { "enum": ["on_enter_pressed", "on_character_entered"] }
        }
      }
    },

    "conversation_filter_object": {
      "description": "Filter object for conversations_select / multi_conversations_select. At least one of include / exclude_external_shared_channels / exclude_bot_users must be present.",
      "type": "object",
      "additionalProperties": false,
      "minProperties": 1,
      "properties": {
        "include": {
          "type": "array",
          "minItems": 1,
          "uniqueItems": true,
          "items": { "enum": ["im", "mpim", "private", "public"] }
        },
        "exclude_external_shared_channels": { "type": "boolean" },
        "exclude_bot_users": { "type": "boolean" }
      }
    },

    "trigger_object": {
      "type": "object",
      "additionalProperties": false,
      "required": ["url"],
      "properties": {
        "url": { "type": "string", "format": "uri" },
        "customizable_input_parameters": {
          "type": "array",
          "items": {
            "type": "object",
            "additionalProperties": false,
            "required": ["name", "value"],
            "properties": {
              "name": { "type": "string", "minLength": 1 },
              "value": {}
            }
          }
        }
      }
    },

    "workflow_object": {
      "type": "object",
      "additionalProperties": false,
      "required": ["trigger"],
      "properties": {
        "trigger": { "$ref": "#/$defs/trigger_object" }
      }
    },

    "placeholder_object": {
      "description": "Reusable placeholder text object (plain_text only, max 150 chars).",
      "allOf": [{ "$ref": "#/$defs/plain_text_object" }, { "properties": { "text": { "maxLength": 150 } } }]
    },

    "button_element": {
      "type": "object",
      "additionalProperties": false,
      "required": ["type", "text"],
      "properties": {
        "type": { "const": "button" },
        "text": {
          "allOf": [{ "$ref": "#/$defs/plain_text_object" }, { "properties": { "text": { "maxLength": 75 } } }]
        },
        "action_id": { "$ref": "#/$defs/action_id" },
        "url": { "type": "string", "format": "uri", "maxLength": 3000 },
        "value": { "type": "string", "minLength": 1, "maxLength": 2000 },
        "style": { "enum": ["primary", "danger"] },
        "confirm": { "$ref": "#/$defs/confirm_object" },
        "accessibility_label": {
          "type": "string",
          "minLength": 1,
          "maxLength": 75
        }
      }
    },

    "icon_button_element": {
      "description": "Icon button — only valid inside a context_actions block.",
      "type": "object",
      "additionalProperties": false,
      "required": ["type", "icon", "text"],
      "properties": {
        "type": { "const": "icon_button" },
        "icon": { "enum": ["trash"] },
        "text": {
          "allOf": [{ "$ref": "#/$defs/plain_text_object" }, { "properties": { "text": { "maxLength": 75 } } }]
        },
        "action_id": { "$ref": "#/$defs/action_id" },
        "value": { "type": "string", "minLength": 1, "maxLength": 2000 },
        "confirm": { "$ref": "#/$defs/confirm_object" },
        "accessibility_label": {
          "type": "string",
          "minLength": 1,
          "maxLength": 75
        },
        "visible_to_user_ids": {
          "type": "array",
          "items": { "type": "string", "pattern": "^[UW][A-Z0-9]+$" }
        }
      }
    },

    "checkboxes_element": {
      "type": "object",
      "additionalProperties": false,
      "required": ["type", "options"],
      "properties": {
        "type": { "const": "checkboxes" },
        "action_id": { "$ref": "#/$defs/action_id" },
        "options": {
          "type": "array",
          "minItems": 1,
          "maxItems": 10,
          "items": { "$ref": "#/$defs/option_object_radio_or_checkbox" }
        },
        "initial_options": {
          "type": "array",
          "minItems": 1,
          "items": { "$ref": "#/$defs/option_object_radio_or_checkbox" }
        },
        "confirm": { "$ref": "#/$defs/confirm_object" },
        "focus_on_load": { "type": "boolean" }
      }
    },

    "datepicker_element": {
      "type": "object",
      "additionalProperties": false,
      "required": ["type"],
      "properties": {
        "type": { "const": "datepicker" },
        "action_id": { "$ref": "#/$defs/action_id" },
        "initial_date": {
          "type": "string",
          "pattern": "^[0-9]{4}-(0[1-9]|1[0-2])-(0[1-9]|[12][0-9]|3[01])$"
        },
        "confirm": { "$ref": "#/$defs/confirm_object" },
        "focus_on_load": { "type": "boolean" },
        "placeholder": { "$ref": "#/$defs/placeholder_object" }
      }
    },

    "datetimepicker_element": {
      "type": "object",
      "additionalProperties": false,
      "required": ["type"],
      "properties": {
        "type": { "const": "datetimepicker" },
        "action_id": { "$ref": "#/$defs/action_id" },
        "initial_date_time": {
          "type": "integer",
          "minimum": 0,
          "maximum": 9999999999
        },
        "confirm": { "$ref": "#/$defs/confirm_object" },
        "focus_on_load": { "type": "boolean" }
      }
    },

    "timepicker_element": {
      "type": "object",
      "additionalProperties": false,
      "required": ["type"],
      "properties": {
        "type": { "const": "timepicker" },
        "action_id": { "$ref": "#/$defs/action_id" },
        "initial_time": {
          "type": "string",
          "pattern": "^([01][0-9]|2[0-3]):[0-5][0-9]$"
        },
        "confirm": { "$ref": "#/$defs/confirm_object" },
        "focus_on_load": { "type": "boolean" },
        "placeholder": { "$ref": "#/$defs/placeholder_object" },
        "timezone": { "type": "string", "minLength": 1 }
      }
    },

    "email_input_element": {
      "description": "Must be used inside an input block.",
      "type": "object",
      "additionalProperties": false,
      "required": ["type"],
      "properties": {
        "type": { "const": "email_text_input" },
        "action_id": { "$ref": "#/$defs/action_id" },
        "initial_value": { "type": "string" },
        "dispatch_action_config": {
          "$ref": "#/$defs/dispatch_action_config_object"
        },
        "focus_on_load": { "type": "boolean" },
        "placeholder": { "$ref": "#/$defs/placeholder_object" }
      }
    },

    "url_input_element": {
      "description": "Must be used inside an input block.",
      "type": "object",
      "additionalProperties": false,
      "required": ["type"],
      "properties": {
        "type": { "const": "url_text_input" },
        "action_id": { "$ref": "#/$defs/action_id" },
        "initial_value": { "type": "string" },
        "dispatch_action_config": {
          "$ref": "#/$defs/dispatch_action_config_object"
        },
        "focus_on_load": { "type": "boolean" },
        "placeholder": { "$ref": "#/$defs/placeholder_object" }
      }
    },

    "number_input_element": {
      "description": "Must be used inside an input block. min_value must not exceed max_value.",
      "type": "object",
      "additionalProperties": false,
      "required": ["type", "is_decimal_allowed"],
      "properties": {
        "type": { "const": "number_input" },
        "is_decimal_allowed": { "type": "boolean" },
        "action_id": { "$ref": "#/$defs/action_id" },
        "initial_value": {
          "type": "string",
          "pattern": "^-?[0-9]+(\\.[0-9]+)?$"
        },
        "min_value": { "type": "string", "pattern": "^-?[0-9]+(\\.[0-9]+)?$" },
        "max_value": { "type": "string", "pattern": "^-?[0-9]+(\\.[0-9]+)?$" },
        "dispatch_action_config": {
          "$ref": "#/$defs/dispatch_action_config_object"
        },
        "focus_on_load": { "type": "boolean" },
        "placeholder": { "$ref": "#/$defs/placeholder_object" }
      }
    },

    "plain_text_input_element": {
      "description": "Must be used inside an input block.",
      "type": "object",
      "additionalProperties": false,
      "required": ["type"],
      "properties": {
        "type": { "const": "plain_text_input" },
        "action_id": { "$ref": "#/$defs/action_id" },
        "initial_value": { "type": "string" },
        "multiline": { "type": "boolean" },
        "min_length": { "type": "integer", "minimum": 0, "maximum": 3000 },
        "max_length": { "type": "integer", "minimum": 1, "maximum": 3000 },
        "dispatch_action_config": {
          "$ref": "#/$defs/dispatch_action_config_object"
        },
        "focus_on_load": { "type": "boolean" },
        "placeholder": { "$ref": "#/$defs/placeholder_object" }
      }
    },

    "radio_buttons_element": {
      "type": "object",
      "additionalProperties": false,
      "required": ["type", "options"],
      "properties": {
        "type": { "const": "radio_buttons" },
        "action_id": { "$ref": "#/$defs/action_id" },
        "options": {
          "type": "array",
          "minItems": 1,
          "maxItems": 10,
          "items": { "$ref": "#/$defs/option_object_radio_or_checkbox" }
        },
        "initial_option": { "$ref": "#/$defs/option_object_radio_or_checkbox" },
        "confirm": { "$ref": "#/$defs/confirm_object" },
        "focus_on_load": { "type": "boolean" }
      }
    },

    "feedback_button_subobject": {
      "type": "object",
      "additionalProperties": false,
      "required": ["text", "value"],
      "properties": {
        "text": {
          "allOf": [{ "$ref": "#/$defs/plain_text_object" }, { "properties": { "text": { "maxLength": 75 } } }]
        },
        "value": { "type": "string", "minLength": 1, "maxLength": 2000 },
        "accessibility_label": {
          "type": "string",
          "minLength": 1,
          "maxLength": 75
        }
      }
    },

    "feedback_buttons_element": {
      "description": "Must be used inside a context_actions block.",
      "type": "object",
      "additionalProperties": false,
      "required": ["type", "positive_button", "negative_button"],
      "properties": {
        "type": { "const": "feedback_buttons" },
        "positive_button": { "$ref": "#/$defs/feedback_button_subobject" },
        "negative_button": { "$ref": "#/$defs/feedback_button_subobject" },
        "action_id": { "$ref": "#/$defs/action_id" }
      }
    },

    "workflow_button_element": {
      "type": "object",
      "additionalProperties": false,
      "required": ["type", "text", "workflow", "action_id"],
      "properties": {
        "type": { "const": "workflow_button" },
        "text": {
          "allOf": [{ "$ref": "#/$defs/plain_text_object" }, { "properties": { "text": { "maxLength": 75 } } }]
        },
        "workflow": { "$ref": "#/$defs/workflow_object" },
        "action_id": { "$ref": "#/$defs/action_id" },
        "style": { "enum": ["primary", "danger"] },
        "accessibility_label": {
          "type": "string",
          "minLength": 1,
          "maxLength": 75
        }
      }
    },

    "static_select_element": {
      "type": "object",
      "additionalProperties": false,
      "required": ["type"],
      "oneOf": [
        { "required": ["options"], "not": { "required": ["option_groups"] } },
        { "required": ["option_groups"], "not": { "required": ["options"] } }
      ],
      "properties": {
        "type": { "const": "static_select" },
        "action_id": { "$ref": "#/$defs/action_id" },
        "options": {
          "type": "array",
          "minItems": 1,
          "maxItems": 100,
          "items": { "$ref": "#/$defs/option_object_plain_text" }
        },
        "option_groups": {
          "type": "array",
          "minItems": 1,
          "maxItems": 100,
          "items": { "$ref": "#/$defs/option_group_object" }
        },
        "initial_option": { "$ref": "#/$defs/option_object_plain_text" },
        "confirm": { "$ref": "#/$defs/confirm_object" },
        "focus_on_load": { "type": "boolean" },
        "placeholder": { "$ref": "#/$defs/placeholder_object" }
      }
    },

    "external_select_element": {
      "type": "object",
      "additionalProperties": false,
      "required": ["type"],
      "properties": {
        "type": { "const": "external_select" },
        "action_id": { "$ref": "#/$defs/action_id" },
        "initial_option": { "$ref": "#/$defs/option_object_plain_text" },
        "min_query_length": { "type": "integer", "minimum": 0 },
        "confirm": { "$ref": "#/$defs/confirm_object" },
        "focus_on_load": { "type": "boolean" },
        "placeholder": { "$ref": "#/$defs/placeholder_object" }
      }
    },

    "users_select_element": {
      "type": "object",
      "additionalProperties": false,
      "required": ["type"],
      "properties": {
        "type": { "const": "users_select" },
        "action_id": { "$ref": "#/$defs/action_id" },
        "initial_user": { "type": "string", "pattern": "^[UW][A-Z0-9]+$" },
        "confirm": { "$ref": "#/$defs/confirm_object" },
        "focus_on_load": { "type": "boolean" },
        "placeholder": { "$ref": "#/$defs/placeholder_object" }
      }
    },

    "conversations_select_element": {
      "description": "response_url_enabled is only valid when used inside an input block within a modal.",
      "type": "object",
      "additionalProperties": false,
      "required": ["type"],
      "properties": {
        "type": { "const": "conversations_select" },
        "action_id": { "$ref": "#/$defs/action_id" },
        "initial_conversation": { "type": "string", "minLength": 1 },
        "default_to_current_conversation": { "type": "boolean" },
        "confirm": { "$ref": "#/$defs/confirm_object" },
        "response_url_enabled": { "type": "boolean" },
        "filter": { "$ref": "#/$defs/conversation_filter_object" },
        "focus_on_load": { "type": "boolean" },
        "placeholder": { "$ref": "#/$defs/placeholder_object" }
      }
    },

    "channels_select_element": {
      "description": "response_url_enabled is only valid when used inside an input block within a modal.",
      "type": "object",
      "additionalProperties": false,
      "required": ["type"],
      "properties": {
        "type": { "const": "channels_select" },
        "action_id": { "$ref": "#/$defs/action_id" },
        "initial_channel": { "type": "string", "pattern": "^[CG][A-Z0-9]+$" },
        "confirm": { "$ref": "#/$defs/confirm_object" },
        "response_url_enabled": { "type": "boolean" },
        "focus_on_load": { "type": "boolean" },
        "placeholder": { "$ref": "#/$defs/placeholder_object" }
      }
    },

    "multi_static_select_element": {
      "type": "object",
      "additionalProperties": false,
      "required": ["type"],
      "oneOf": [
        { "required": ["options"], "not": { "required": ["option_groups"] } },
        { "required": ["option_groups"], "not": { "required": ["options"] } }
      ],
      "properties": {
        "type": { "const": "multi_static_select" },
        "action_id": { "$ref": "#/$defs/action_id" },
        "options": {
          "type": "array",
          "minItems": 1,
          "maxItems": 100,
          "items": { "$ref": "#/$defs/option_object_plain_text" }
        },
        "option_groups": {
          "type": "array",
          "minItems": 1,
          "maxItems": 100,
          "items": { "$ref": "#/$defs/option_group_object" }
        },
        "initial_options": {
          "type": "array",
          "minItems": 1,
          "items": { "$ref": "#/$defs/option_object_plain_text" }
        },
        "confirm": { "$ref": "#/$defs/confirm_object" },
        "max_selected_items": { "type": "integer", "minimum": 1 },
        "focus_on_load": { "type": "boolean" },
        "placeholder": { "$ref": "#/$defs/placeholder_object" }
      }
    },

    "multi_external_select_element": {
      "type": "object",
      "additionalProperties": false,
      "required": ["type"],
      "properties": {
        "type": { "const": "multi_external_select" },
        "action_id": { "$ref": "#/$defs/action_id" },
        "min_query_length": { "type": "integer", "minimum": 0 },
        "initial_options": {
          "type": "array",
          "minItems": 1,
          "items": { "$ref": "#/$defs/option_object_plain_text" }
        },
        "confirm": { "$ref": "#/$defs/confirm_object" },
        "max_selected_items": { "type": "integer", "minimum": 1 },
        "focus_on_load": { "type": "boolean" },
        "placeholder": { "$ref": "#/$defs/placeholder_object" }
      }
    },

    "multi_users_select_element": {
      "type": "object",
      "additionalProperties": false,
      "required": ["type"],
      "properties": {
        "type": { "const": "multi_users_select" },
        "action_id": { "$ref": "#/$defs/action_id" },
        "initial_users": {
          "type": "array",
          "minItems": 1,
          "items": { "type": "string", "pattern": "^[UW][A-Z0-9]+$" }
        },
        "confirm": { "$ref": "#/$defs/confirm_object" },
        "max_selected_items": { "type": "integer", "minimum": 1 },
        "focus_on_load": { "type": "boolean" },
        "placeholder": { "$ref": "#/$defs/placeholder_object" }
      }
    },

    "multi_conversations_select_element": {
      "type": "object",
      "additionalProperties": false,
      "required": ["type"],
      "properties": {
        "type": { "const": "multi_conversations_select" },
        "action_id": { "$ref": "#/$defs/action_id" },
        "initial_conversations": {
          "type": "array",
          "minItems": 1,
          "items": { "type": "string", "minLength": 1 }
        },
        "default_to_current_conversation": { "type": "boolean" },
        "confirm": { "$ref": "#/$defs/confirm_object" },
        "max_selected_items": { "type": "integer", "minimum": 1 },
        "filter": { "$ref": "#/$defs/conversation_filter_object" },
        "focus_on_load": { "type": "boolean" },
        "placeholder": { "$ref": "#/$defs/placeholder_object" }
      }
    },

    "multi_channels_select_element": {
      "type": "object",
      "additionalProperties": false,
      "required": ["type"],
      "properties": {
        "type": { "const": "multi_channels_select" },
        "action_id": { "$ref": "#/$defs/action_id" },
        "initial_channels": {
          "type": "array",
          "minItems": 1,
          "items": { "type": "string", "pattern": "^[CG][A-Z0-9]+$" }
        },
        "confirm": { "$ref": "#/$defs/confirm_object" },
        "max_selected_items": { "type": "integer", "minimum": 1 },
        "focus_on_load": { "type": "boolean" },
        "placeholder": { "$ref": "#/$defs/placeholder_object" }
      }
    },

    "overflow_element": {
      "description": "Must be used inside a section or actions block. Up to 5 options.",
      "type": "object",
      "additionalProperties": false,
      "required": ["type", "options"],
      "properties": {
        "type": { "const": "overflow" },
        "action_id": { "$ref": "#/$defs/action_id" },
        "options": {
          "type": "array",
          "minItems": 1,
          "maxItems": 5,
          "items": { "$ref": "#/$defs/option_object_overflow" }
        },
        "confirm": { "$ref": "#/$defs/confirm_object" }
      }
    },

    "rich_text_input_element": {
      "description": "Must be used inside an input block.",
      "type": "object",
      "additionalProperties": false,
      "required": ["type", "action_id"],
      "properties": {
        "type": { "const": "rich_text_input" },
        "action_id": { "$ref": "#/$defs/action_id" },
        "initial_value": { "$ref": "#/$defs/rich_text_block" },
        "dispatch_action_config": {
          "$ref": "#/$defs/dispatch_action_config_object"
        },
        "focus_on_load": { "type": "boolean" },
        "placeholder": { "$ref": "#/$defs/placeholder_object" }
      }
    },

    "file_input_element": {
      "description": "Must be used inside an input block in modals only. Requires files:read OAuth scope. 10MB per-file limit (not enforceable in JSON Schema).",
      "type": "object",
      "additionalProperties": false,
      "required": ["type"],
      "properties": {
        "type": { "const": "file_input" },
        "action_id": { "$ref": "#/$defs/action_id" },
        "filetypes": {
          "type": "array",
          "minItems": 1,
          "items": { "type": "string", "minLength": 1 }
        },
        "max_files": { "type": "integer", "minimum": 1, "maximum": 10 }
      }
    },

    "image_element": {
      "description": "Must be used inside a section or context block. Either image_url or slack_file is required.",
      "type": "object",
      "additionalProperties": false,
      "required": ["type", "alt_text"],
      "oneOf": [
        { "required": ["image_url"], "not": { "required": ["slack_file"] } },
        { "required": ["slack_file"], "not": { "required": ["image_url"] } }
      ],
      "properties": {
        "type": { "const": "image" },
        "alt_text": { "type": "string", "minLength": 1 },
        "image_url": { "type": "string", "format": "uri", "maxLength": 3000 },
        "slack_file": { "$ref": "#/$defs/slack_file_object" }
      }
    },

    "url_source_element": {
      "description": "URL source element — only valid inside a task_card block's sources array.",
      "type": "object",
      "additionalProperties": false,
      "required": ["type", "url", "text"],
      "properties": {
        "type": { "const": "url" },
        "url": { "type": "string", "format": "uri" },
        "text": { "type": "string", "minLength": 1 }
      }
    },

    "actions_block_element": {
      "description": "Elements allowed inside an actions block.",
      "oneOf": [
        { "$ref": "#/$defs/button_element" },
        { "$ref": "#/$defs/checkboxes_element" },
        { "$ref": "#/$defs/datepicker_element" },
        { "$ref": "#/$defs/datetimepicker_element" },
        { "$ref": "#/$defs/timepicker_element" },
        { "$ref": "#/$defs/overflow_element" },
        { "$ref": "#/$defs/radio_buttons_element" },
        { "$ref": "#/$defs/static_select_element" },
        { "$ref": "#/$defs/external_select_element" },
        { "$ref": "#/$defs/users_select_element" },
        { "$ref": "#/$defs/conversations_select_element" },
        { "$ref": "#/$defs/channels_select_element" },
        { "$ref": "#/$defs/multi_static_select_element" },
        { "$ref": "#/$defs/multi_external_select_element" },
        { "$ref": "#/$defs/multi_users_select_element" },
        { "$ref": "#/$defs/multi_conversations_select_element" },
        { "$ref": "#/$defs/multi_channels_select_element" },
        { "$ref": "#/$defs/workflow_button_element" }
      ]
    },

    "section_accessory_element": {
      "description": "Elements that may appear as the accessory of a section block. datetimepicker is intentionally excluded — docs say it 'must be used inside the actions block or input block'.",
      "oneOf": [
        { "$ref": "#/$defs/button_element" },
        { "$ref": "#/$defs/checkboxes_element" },
        { "$ref": "#/$defs/datepicker_element" },
        { "$ref": "#/$defs/timepicker_element" },
        { "$ref": "#/$defs/image_element" },
        { "$ref": "#/$defs/overflow_element" },
        { "$ref": "#/$defs/radio_buttons_element" },
        { "$ref": "#/$defs/static_select_element" },
        { "$ref": "#/$defs/external_select_element" },
        { "$ref": "#/$defs/users_select_element" },
        { "$ref": "#/$defs/conversations_select_element" },
        { "$ref": "#/$defs/channels_select_element" },
        { "$ref": "#/$defs/multi_static_select_element" },
        { "$ref": "#/$defs/multi_external_select_element" },
        { "$ref": "#/$defs/multi_users_select_element" },
        { "$ref": "#/$defs/multi_conversations_select_element" },
        { "$ref": "#/$defs/multi_channels_select_element" },
        { "$ref": "#/$defs/workflow_button_element" }
      ]
    },

    "input_block_element": {
      "description": "Elements that may appear as the element of an input block.",
      "oneOf": [
        { "$ref": "#/$defs/plain_text_input_element" },
        { "$ref": "#/$defs/email_input_element" },
        { "$ref": "#/$defs/url_input_element" },
        { "$ref": "#/$defs/number_input_element" },
        { "$ref": "#/$defs/checkboxes_element" },
        { "$ref": "#/$defs/radio_buttons_element" },
        { "$ref": "#/$defs/datepicker_element" },
        { "$ref": "#/$defs/datetimepicker_element" },
        { "$ref": "#/$defs/timepicker_element" },
        { "$ref": "#/$defs/static_select_element" },
        { "$ref": "#/$defs/external_select_element" },
        { "$ref": "#/$defs/users_select_element" },
        { "$ref": "#/$defs/conversations_select_element" },
        { "$ref": "#/$defs/channels_select_element" },
        { "$ref": "#/$defs/multi_static_select_element" },
        { "$ref": "#/$defs/multi_external_select_element" },
        { "$ref": "#/$defs/multi_users_select_element" },
        { "$ref": "#/$defs/multi_conversations_select_element" },
        { "$ref": "#/$defs/multi_channels_select_element" },
        { "$ref": "#/$defs/rich_text_input_element" },
        { "$ref": "#/$defs/file_input_element" }
      ]
    },

    "context_block_element": {
      "description": "Elements allowed inside a context block.",
      "oneOf": [{ "$ref": "#/$defs/image_element" }, { "$ref": "#/$defs/text_object" }]
    },

    "context_actions_block_element": {
      "description": "Elements allowed inside a context_actions block.",
      "oneOf": [{ "$ref": "#/$defs/feedback_buttons_element" }, { "$ref": "#/$defs/icon_button_element" }]
    },

    "rich_text_style_object": {
      "description": "Style flags for rich-text leaf elements. Slack docs disagree on which flags are allowed per leaf type; this is the union of all flags documented.",
      "type": "object",
      "additionalProperties": false,
      "minProperties": 1,
      "properties": {
        "bold": { "type": "boolean" },
        "italic": { "type": "boolean" },
        "strike": { "type": "boolean" },
        "underline": { "type": "boolean" },
        "code": { "type": "boolean" },
        "highlight": { "type": "boolean" },
        "client_highlight": { "type": "boolean" },
        "unlink": { "type": "boolean" }
      }
    },

    "rich_text_text_leaf": {
      "type": "object",
      "additionalProperties": false,
      "required": ["type", "text"],
      "properties": {
        "type": { "const": "text" },
        "text": { "type": "string" },
        "style": { "$ref": "#/$defs/rich_text_style_object" }
      }
    },

    "rich_text_link_leaf": {
      "type": "object",
      "additionalProperties": false,
      "required": ["type", "url"],
      "properties": {
        "type": { "const": "link" },
        "url": { "type": "string", "format": "uri" },
        "text": { "type": "string" },
        "unsafe": { "type": "boolean" },
        "style": { "$ref": "#/$defs/rich_text_style_object" }
      }
    },

    "rich_text_user_leaf": {
      "type": "object",
      "additionalProperties": false,
      "required": ["type", "user_id"],
      "properties": {
        "type": { "const": "user" },
        "user_id": { "type": "string", "pattern": "^[UW][A-Z0-9]+$" },
        "style": { "$ref": "#/$defs/rich_text_style_object" }
      }
    },

    "rich_text_usergroup_leaf": {
      "type": "object",
      "additionalProperties": false,
      "required": ["type", "usergroup_id"],
      "properties": {
        "type": { "const": "usergroup" },
        "usergroup_id": { "type": "string", "pattern": "^S[A-Z0-9]+$" },
        "style": { "$ref": "#/$defs/rich_text_style_object" }
      }
    },

    "rich_text_channel_leaf": {
      "type": "object",
      "additionalProperties": false,
      "required": ["type", "channel_id"],
      "properties": {
        "type": { "const": "channel" },
        "channel_id": { "type": "string", "pattern": "^[CG][A-Z0-9]+$" },
        "style": { "$ref": "#/$defs/rich_text_style_object" }
      }
    },

    "rich_text_emoji_leaf": {
      "description": "Slack's official docs (rich-text-block reference) only list type/name/unicode, but the API silently accepts a `style` object on emoji leaves. We allow it to match observed behavior.",
      "type": "object",
      "additionalProperties": false,
      "required": ["type", "name"],
      "properties": {
        "type": { "const": "emoji" },
        "name": { "type": "string", "minLength": 1 },
        "skin_tone": { "type": "integer", "minimum": 1, "maximum": 6 },
        "unicode": { "type": "string", "minLength": 1 },
        "style": { "$ref": "#/$defs/rich_text_style_object" }
      }
    },

    "rich_text_team_leaf": {
      "description": "Whole-team mention (e.g. <!T12345>) — referenced by team_id.",
      "type": "object",
      "additionalProperties": false,
      "required": ["type", "team_id"],
      "properties": {
        "type": { "const": "team" },
        "team_id": { "type": "string", "pattern": "^T[A-Z0-9]+$" },
        "style": { "$ref": "#/$defs/rich_text_style_object" }
      }
    },

    "rich_text_broadcast_leaf": {
      "type": "object",
      "additionalProperties": false,
      "required": ["type", "range"],
      "properties": {
        "type": { "const": "broadcast" },
        "range": { "enum": ["here", "channel", "everyone"] },
        "style": { "$ref": "#/$defs/rich_text_style_object" }
      }
    },

    "rich_text_color_leaf": {
      "type": "object",
      "additionalProperties": false,
      "required": ["type", "value"],
      "properties": {
        "type": { "const": "color" },
        "value": { "type": "string", "pattern": "^#?[0-9a-fA-F]{6}$" },
        "style": { "$ref": "#/$defs/rich_text_style_object" }
      }
    },

    "rich_text_date_leaf": {
      "type": "object",
      "additionalProperties": false,
      "required": ["type", "timestamp", "format"],
      "properties": {
        "type": { "const": "date" },
        "timestamp": { "type": "integer", "minimum": 0 },
        "format": { "type": "string", "minLength": 1 },
        "url": { "type": "string", "format": "uri" },
        "fallback": { "type": "string" },
        "style": { "$ref": "#/$defs/rich_text_style_object" }
      }
    },

    "rich_text_leaf": {
      "description": "Any of the 10 rich-text leaf element kinds.",
      "oneOf": [
        { "$ref": "#/$defs/rich_text_text_leaf" },
        { "$ref": "#/$defs/rich_text_link_leaf" },
        { "$ref": "#/$defs/rich_text_user_leaf" },
        { "$ref": "#/$defs/rich_text_usergroup_leaf" },
        { "$ref": "#/$defs/rich_text_team_leaf" },
        { "$ref": "#/$defs/rich_text_channel_leaf" },
        { "$ref": "#/$defs/rich_text_emoji_leaf" },
        { "$ref": "#/$defs/rich_text_broadcast_leaf" },
        { "$ref": "#/$defs/rich_text_color_leaf" },
        { "$ref": "#/$defs/rich_text_date_leaf" }
      ]
    },

    "rich_text_section_element": {
      "type": "object",
      "additionalProperties": false,
      "required": ["type", "elements"],
      "properties": {
        "type": { "const": "rich_text_section" },
        "elements": {
          "description": "Empty array is accepted by Slack (verified in Block Kit Builder 2026-04-16).",
          "type": "array",
          "items": { "$ref": "#/$defs/rich_text_leaf" }
        }
      }
    },

    "rich_text_list_element": {
      "type": "object",
      "additionalProperties": false,
      "required": ["type", "style", "elements"],
      "properties": {
        "type": { "const": "rich_text_list" },
        "style": { "enum": ["bullet", "ordered"] },
        "elements": {
          "type": "array",
          "minItems": 1,
          "items": { "$ref": "#/$defs/rich_text_section_element" }
        },
        "indent": { "type": "integer", "minimum": 0 },
        "offset": { "type": "integer", "minimum": 0 },
        "border": { "type": "integer", "enum": [0, 1] }
      }
    },

    "rich_text_preformatted_element": {
      "type": "object",
      "additionalProperties": false,
      "required": ["type", "elements"],
      "properties": {
        "type": { "const": "rich_text_preformatted" },
        "elements": {
          "description": "Empty array is accepted by Slack (verified in Block Kit Builder 2026-04-16).",
          "type": "array",
          "items": { "$ref": "#/$defs/rich_text_leaf" }
        },
        "border": { "type": "integer", "enum": [0, 1] },
        "language": { "type": "string", "minLength": 1 }
      }
    },

    "rich_text_quote_element": {
      "type": "object",
      "additionalProperties": false,
      "required": ["type", "elements"],
      "properties": {
        "type": { "const": "rich_text_quote" },
        "elements": {
          "description": "Empty array is accepted by Slack (verified in Block Kit Builder 2026-04-16).",
          "type": "array",
          "items": { "$ref": "#/$defs/rich_text_leaf" }
        },
        "border": { "type": "integer", "enum": [0, 1] }
      }
    },

    "rich_text_container_element": {
      "description": "Any of the 4 rich-text container kinds usable inside a rich_text block's elements array.",
      "oneOf": [
        { "$ref": "#/$defs/rich_text_section_element" },
        { "$ref": "#/$defs/rich_text_list_element" },
        { "$ref": "#/$defs/rich_text_preformatted_element" },
        { "$ref": "#/$defs/rich_text_quote_element" }
      ]
    },

    "actions_block": {
      "type": "object",
      "additionalProperties": false,
      "required": ["type", "elements"],
      "properties": {
        "type": { "const": "actions" },
        "elements": {
          "type": "array",
          "minItems": 1,
          "maxItems": 25,
          "items": { "$ref": "#/$defs/actions_block_element" }
        },
        "block_id": { "$ref": "#/$defs/block_id" }
      }
    },

    "alert_block": {
      "type": "object",
      "additionalProperties": false,
      "required": ["type", "text"],
      "properties": {
        "type": { "const": "alert" },
        "text": { "$ref": "#/$defs/text_object" },
        "level": { "enum": ["default", "info", "warning", "error", "success"] },
        "block_id": { "$ref": "#/$defs/block_id" }
      }
    },

    "card_block": {
      "description": "At least one of hero_image, title, actions, or body is required.",
      "type": "object",
      "additionalProperties": false,
      "required": ["type"],
      "anyOf": [
        { "required": ["hero_image"] },
        { "required": ["title"] },
        { "required": ["actions"] },
        { "required": ["body"] }
      ],
      "properties": {
        "type": { "const": "card" },
        "block_id": { "$ref": "#/$defs/block_id" },
        "hero_image": { "$ref": "#/$defs/image_element" },
        "icon": { "$ref": "#/$defs/image_element" },
        "title": {
          "allOf": [{ "$ref": "#/$defs/text_object" }, { "properties": { "text": { "maxLength": 150 } } }]
        },
        "subtitle": {
          "allOf": [{ "$ref": "#/$defs/text_object" }, { "properties": { "text": { "maxLength": 150 } } }]
        },
        "body": {
          "allOf": [{ "$ref": "#/$defs/text_object" }, { "properties": { "text": { "maxLength": 200 } } }]
        },
        "actions": {
          "type": "array",
          "minItems": 1,
          "maxItems": 2,
          "items": { "$ref": "#/$defs/button_element" }
        }
      }
    },

    "carousel_block": {
      "type": "object",
      "additionalProperties": false,
      "required": ["type", "elements"],
      "properties": {
        "type": { "const": "carousel" },
        "elements": {
          "type": "array",
          "minItems": 1,
          "maxItems": 10,
          "items": { "$ref": "#/$defs/card_block" }
        },
        "block_id": { "$ref": "#/$defs/block_id" }
      }
    },

    "container_child_block": {
      "description": "A block allowed inside a container block's child_blocks array. Slack documents this set as: actions, context, divider, file, header, image, input, rich_text, section, table, video (https://docs.slack.dev/reference/block-kit/blocks/container-block). Notably excludes container itself (no nesting) and message-only chrome like card/carousel/markdown.",
      "oneOf": [
        { "$ref": "#/$defs/actions_block" },
        { "$ref": "#/$defs/context_block" },
        { "$ref": "#/$defs/divider_block" },
        { "$ref": "#/$defs/file_block" },
        { "$ref": "#/$defs/header_block" },
        { "$ref": "#/$defs/image_block" },
        { "$ref": "#/$defs/input_block" },
        { "$ref": "#/$defs/rich_text_block" },
        { "$ref": "#/$defs/section_block" },
        { "$ref": "#/$defs/table_block" },
        { "$ref": "#/$defs/video_block" }
      ]
    },

    "container_block": {
      "description": "A general-purpose wrapper that groups child blocks into a single, optionally collapsible unit with a configurable width. Messages only (https://docs.slack.dev/reference/block-kit/blocks/container-block). default_collapsed only takes effect when is_collapsible is true; the schema rejects default_collapsed: true without is_collapsible: true.",
      "type": "object",
      "additionalProperties": false,
      "required": ["type", "title", "child_blocks"],
      "properties": {
        "type": { "const": "container" },
        "block_id": { "$ref": "#/$defs/block_id" },
        "title": {
          "allOf": [{ "$ref": "#/$defs/plain_text_object" }, { "properties": { "text": { "maxLength": 150 } } }]
        },
        "subtitle": {
          "allOf": [{ "$ref": "#/$defs/plain_text_object" }, { "properties": { "text": { "maxLength": 150 } } }]
        },
        "icon": { "$ref": "#/$defs/image_element" },
        "width": { "enum": ["narrow", "standard", "wide", "full"] },
        "is_collapsible": { "type": "boolean" },
        "default_collapsed": { "type": "boolean" },
        "child_blocks": {
          "type": "array",
          "minItems": 1,
          "maxItems": 10,
          "items": { "$ref": "#/$defs/container_child_block" }
        }
      },
      "if": {
        "properties": { "default_collapsed": { "const": true } },
        "required": ["default_collapsed"]
      },
      "then": {
        "properties": { "is_collapsible": { "const": true } },
        "required": ["is_collapsible"]
      }
    },

    "context_actions_block": {
      "type": "object",
      "additionalProperties": false,
      "required": ["type", "elements"],
      "properties": {
        "type": { "const": "context_actions" },
        "elements": {
          "type": "array",
          "minItems": 1,
          "maxItems": 5,
          "items": { "$ref": "#/$defs/context_actions_block_element" }
        },
        "block_id": { "$ref": "#/$defs/block_id" }
      }
    },

    "context_block": {
      "type": "object",
      "additionalProperties": false,
      "required": ["type", "elements"],
      "properties": {
        "type": { "const": "context" },
        "elements": {
          "type": "array",
          "minItems": 1,
          "maxItems": 10,
          "items": { "$ref": "#/$defs/context_block_element" }
        },
        "block_id": { "$ref": "#/$defs/block_id" }
      }
    },

    "data_visualization_data_point": {
      "description": "A single point in a chart series: an x-axis label and its numeric value. The label must match one of axis_config.categories (enforced via checkDataVisualizationConsistency). Negative values are permitted — line/bar/area charts render against a zero baseline.",
      "type": "object",
      "additionalProperties": false,
      "required": ["label", "value"],
      "properties": {
        "label": { "type": "string", "minLength": 1, "maxLength": 20 },
        "value": { "type": "number" }
      }
    },

    "data_visualization_series": {
      "description": "A named series of data points plotted on a line/bar/area chart. The name drives the chart legend and must be unique across all series in the same chart (enforced via checkDataVisualizationConsistency).",
      "type": "object",
      "additionalProperties": false,
      "required": ["name", "data"],
      "properties": {
        "name": { "type": "string", "minLength": 1, "maxLength": 20 },
        "data": {
          "type": "array",
          "minItems": 1,
          "maxItems": 20,
          "items": { "$ref": "#/$defs/data_visualization_data_point" }
        }
      }
    },

    "data_visualization_axis_config": {
      "description": "Axis configuration for cartesian (line/bar/area) charts. categories define the valid x-axis labels and their left-to-right display order. At most 20 categories — each series must carry exactly one data point per category, and a series' data array is itself capped at 20 items.",
      "type": "object",
      "additionalProperties": false,
      "required": ["categories"],
      "properties": {
        "categories": {
          "type": "array",
          "maxItems": 20,
          "items": { "type": "string", "minLength": 1, "maxLength": 20 }
        },
        "x_label": { "type": "string", "maxLength": 50 },
        "y_label": { "type": "string", "maxLength": 50 }
      }
    },

    "data_visualization_segment": {
      "description": "A single slice of a pie chart. value must be greater than 0; Slack derives the displayed percentage from each segment's value as a share of the total.",
      "type": "object",
      "additionalProperties": false,
      "required": ["label", "value"],
      "properties": {
        "label": { "type": "string", "minLength": 1, "maxLength": 20 },
        "value": { "type": "number", "exclusiveMinimum": 0 }
      }
    },

    "data_visualization_chart": {
      "description": "The chart rendered by a data_visualization block. line/bar/area charts use series + axis_config; pie charts use segments.",
      "oneOf": [
        {
          "description": "Cartesian chart — line, bar, or area. 1–6 series; axis_config required.",
          "type": "object",
          "additionalProperties": false,
          "required": ["type", "series", "axis_config"],
          "properties": {
            "type": { "enum": ["line", "bar", "area"] },
            "series": {
              "type": "array",
              "minItems": 1,
              "maxItems": 6,
              "items": { "$ref": "#/$defs/data_visualization_series" }
            },
            "axis_config": { "$ref": "#/$defs/data_visualization_axis_config" }
          }
        },
        {
          "description": "Pie chart. 1–6 segments.",
          "type": "object",
          "additionalProperties": false,
          "required": ["type", "segments"],
          "properties": {
            "type": { "const": "pie" },
            "segments": {
              "type": "array",
              "minItems": 1,
              "maxItems": 6,
              "items": { "$ref": "#/$defs/data_visualization_segment" }
            }
          }
        }
      ]
    },

    "data_table_cell": {
      "description": "A cell inside a data_table_block row. `raw_text` / `raw_number` for simple values, `rich_text` for formatted content. Per https://docs.slack.dev/reference/block-kit/blocks/data-table-block. The docs' per-cell schemas list `properties` without a `required` array; we mirror `table_cell` and require the value-bearing field(s). The rule 'the first (header) row cannot contain rich_text cells' is a row-position constraint JSON Schema can't express and is not enforced here.",
      "oneOf": [
        {
          "type": "object",
          "additionalProperties": false,
          "required": ["type", "text"],
          "properties": {
            "type": { "const": "raw_text" },
            "text": { "type": "string", "minLength": 1 }
          }
        },
        {
          "type": "object",
          "additionalProperties": false,
          "required": ["type", "value"],
          "properties": {
            "type": { "const": "raw_number" },
            "value": { "type": "number" },
            "text": { "type": "string", "minLength": 1 }
          }
        },
        {
          "type": "object",
          "additionalProperties": false,
          "required": ["type", "elements"],
          "properties": {
            "type": { "const": "rich_text" },
            "elements": {
              "type": "array",
              "items": { "$ref": "#/$defs/rich_text_container_element" }
            }
          }
        }
      ]
    },

    "data_table_block": {
      "description": "Rich, interactive table with pagination, sorting, and filtering (https://docs.slack.dev/reference/block-kit/blocks/data-table-block). Distinct from `table_block`, which is a simpler static table. The single-table and aggregate 10,000-character limits are payload-level rules not enforced here. `row_header_column_index` must point at an existing column, a cross-field rule JSON Schema can't check (bounded to 0–19 since a row has at most 20 cells).",
      "type": "object",
      "additionalProperties": false,
      "required": ["type", "caption", "rows"],
      "properties": {
        "type": { "const": "data_table" },
        "block_id": { "$ref": "#/$defs/block_id" },
        "caption": { "type": "string", "minLength": 1 },
        "page_size": { "type": "integer", "minimum": 1, "maximum": 100 },
        "row_header_column_index": { "type": "integer", "minimum": 0, "maximum": 19 },
        "rows": {
          "description": "First row is the header; 2–101 rows total (1 header + 1–100 data rows), 1–20 cells per row.",
          "type": "array",
          "minItems": 2,
          "maxItems": 101,
          "items": {
            "type": "array",
            "minItems": 1,
            "maxItems": 20,
            "items": { "$ref": "#/$defs/data_table_cell" }
          }
        }
      }
    },

    "data_visualization_block": {
      "description": "Renders data as a line, bar, area, or pie chart. Messages only (https://docs.slack.dev/reference/block-kit/blocks/data-visualization-block). Slack renders at most two data_visualization blocks per message (enforced via the checkDataVisualizationMax helper, since JSON Schema can't count sibling blocks). Two further runtime rules are enforced via checkDataVisualizationConsistency, since they depend on sibling-field values JSON Schema can't compare: series names must be unique within a chart, and each series must contain exactly one data point per axis_config.categories label.",
      "type": "object",
      "additionalProperties": false,
      "required": ["type", "title", "chart"],
      "properties": {
        "type": { "const": "data_visualization" },
        "block_id": { "$ref": "#/$defs/block_id" },
        "title": { "type": "string", "minLength": 1, "maxLength": 50 },
        "chart": { "$ref": "#/$defs/data_visualization_chart" }
      }
    },

    "divider_block": {
      "type": "object",
      "additionalProperties": false,
      "required": ["type"],
      "properties": {
        "type": { "const": "divider" },
        "block_id": { "$ref": "#/$defs/block_id" }
      }
    },

    "file_block": {
      "description": "Cannot be added to app surfaces directly; surfaces only when retrieving messages that contain remote files.",
      "type": "object",
      "additionalProperties": false,
      "required": ["type", "external_id", "source"],
      "properties": {
        "type": { "const": "file" },
        "external_id": { "type": "string", "minLength": 1 },
        "source": { "const": "remote" },
        "block_id": { "$ref": "#/$defs/block_id" }
      }
    },

    "header_block": {
      "type": "object",
      "additionalProperties": false,
      "required": ["type", "text"],
      "properties": {
        "type": { "const": "header" },
        "text": {
          "allOf": [{ "$ref": "#/$defs/plain_text_object" }, { "properties": { "text": { "maxLength": 150 } } }]
        },
        "block_id": { "$ref": "#/$defs/block_id" },
        "level": { "type": "integer", "minimum": 1, "maximum": 4 }
      }
    },

    "image_block": {
      "description": "Either image_url or slack_file is required (not both).",
      "type": "object",
      "additionalProperties": false,
      "required": ["type", "alt_text"],
      "oneOf": [
        { "required": ["image_url"], "not": { "required": ["slack_file"] } },
        { "required": ["slack_file"], "not": { "required": ["image_url"] } }
      ],
      "properties": {
        "type": { "const": "image" },
        "alt_text": { "type": "string", "minLength": 1, "maxLength": 2000 },
        "image_url": { "type": "string", "format": "uri", "maxLength": 3000 },
        "slack_file": { "$ref": "#/$defs/slack_file_object" },
        "title": {
          "allOf": [{ "$ref": "#/$defs/plain_text_object" }, { "properties": { "text": { "maxLength": 2000 } } }]
        },
        "block_id": { "$ref": "#/$defs/block_id" }
      }
    },

    "input_block": {
      "description": "If element is a file_input, dispatch_action must not be true.",
      "type": "object",
      "additionalProperties": false,
      "required": ["type", "label", "element"],
      "properties": {
        "type": { "const": "input" },
        "label": {
          "allOf": [{ "$ref": "#/$defs/plain_text_object" }, { "properties": { "text": { "maxLength": 2000 } } }]
        },
        "element": { "$ref": "#/$defs/input_block_element" },
        "dispatch_action": { "type": "boolean" },
        "block_id": { "$ref": "#/$defs/block_id" },
        "hint": {
          "allOf": [{ "$ref": "#/$defs/plain_text_object" }, { "properties": { "text": { "maxLength": 2000 } } }]
        },
        "optional": { "type": "boolean" }
      },
      "allOf": [
        {
          "if": {
            "properties": {
              "element": {
                "properties": { "type": { "const": "file_input" } },
                "required": ["type"]
              }
            },
            "required": ["element"]
          },
          "then": {
            "properties": { "dispatch_action": { "const": false } }
          }
        }
      ]
    },

    "markdown_block": {
      "description": "block_id is ignored on markdown blocks. Cumulative 12,000-char limit across all markdown blocks in one payload is a payload-level rule, not enforced here.",
      "type": "object",
      "additionalProperties": false,
      "required": ["type", "text"],
      "properties": {
        "type": { "const": "markdown" },
        "text": { "type": "string", "minLength": 1, "maxLength": 12000 },
        "block_id": { "$ref": "#/$defs/block_id" }
      }
    },

    "task_card_inline_object": {
      "description": "A task card as it appears inline within a plan_block tasks array — the docs' example omits the type discriminator.",
      "type": "object",
      "additionalProperties": false,
      "required": ["task_id", "title"],
      "properties": {
        "type": { "const": "task_card" },
        "task_id": { "type": "string", "minLength": 1 },
        "title": { "type": "string", "minLength": 1 },
        "details": { "$ref": "#/$defs/rich_text_block" },
        "output": { "$ref": "#/$defs/rich_text_block" },
        "sources": {
          "type": "array",
          "items": { "$ref": "#/$defs/url_source_element" }
        },
        "status": { "enum": ["pending", "in_progress", "complete", "error"] },
        "block_id": { "$ref": "#/$defs/block_id" }
      }
    },

    "plan_block": {
      "type": "object",
      "additionalProperties": false,
      "required": ["type", "title"],
      "properties": {
        "type": { "const": "plan" },
        "title": {
          "oneOf": [{ "type": "string", "minLength": 1 }, { "$ref": "#/$defs/plain_text_object" }]
        },
        "block_id": { "$ref": "#/$defs/block_id" },
        "tasks": {
          "type": "array",
          "items": { "$ref": "#/$defs/task_card_inline_object" }
        }
      }
    },

    "rich_text_block": {
      "type": "object",
      "additionalProperties": false,
      "required": ["type", "elements"],
      "properties": {
        "type": { "const": "rich_text" },
        "elements": {
          "description": "Empty array is accepted by Slack (verified in Block Kit Builder 2026-04-16).",
          "type": "array",
          "items": { "$ref": "#/$defs/rich_text_container_element" }
        },
        "block_id": { "$ref": "#/$defs/block_id" }
      }
    },

    "section_block": {
      "description": "Must have text or fields (or both).",
      "type": "object",
      "additionalProperties": false,
      "required": ["type"],
      "anyOf": [{ "required": ["text"] }, { "required": ["fields"] }],
      "properties": {
        "type": { "const": "section" },
        "text": { "$ref": "#/$defs/text_object" },
        "block_id": { "$ref": "#/$defs/block_id" },
        "fields": {
          "type": "array",
          "minItems": 1,
          "maxItems": 10,
          "items": {
            "allOf": [{ "$ref": "#/$defs/text_object" }, { "properties": { "text": { "maxLength": 2000 } } }]
          }
        },
        "accessory": { "$ref": "#/$defs/section_accessory_element" },
        "expand": { "type": "boolean" }
      }
    },

    "table_cell": {
      "description": "A cell inside a table_block row. Either raw_text or rich_text.",
      "oneOf": [
        {
          "type": "object",
          "additionalProperties": false,
          "required": ["type", "text"],
          "properties": {
            "type": { "const": "raw_text" },
            "text": { "type": "string" }
          }
        },
        {
          "type": "object",
          "additionalProperties": false,
          "required": ["type", "elements"],
          "properties": {
            "type": { "const": "rich_text" },
            "elements": {
              "description": "Empty array is accepted by Slack (verified in Block Kit Builder 2026-04-16).",
              "type": "array",
              "items": { "$ref": "#/$defs/rich_text_container_element" }
            }
          }
        }
      ]
    },

    "table_column_setting": {
      "description": "Per-column settings inside table_block.column_settings. May be null to skip.",
      "oneOf": [
        { "type": "null" },
        {
          "type": "object",
          "additionalProperties": false,
          "properties": {
            "align": { "enum": ["left", "center", "right"] },
            "is_wrapped": { "type": "boolean" }
          }
        }
      ]
    },

    "table_block": {
      "description": "One table per message (server-enforced via invalid_attachments / only_one_table_allowed). Up to 100 rows, up to 20 cells per row.",
      "type": "object",
      "additionalProperties": false,
      "required": ["type", "rows"],
      "properties": {
        "type": { "const": "table" },
        "block_id": { "$ref": "#/$defs/block_id" },
        "rows": {
          "type": "array",
          "minItems": 1,
          "maxItems": 100,
          "items": {
            "type": "array",
            "minItems": 1,
            "maxItems": 20,
            "items": { "$ref": "#/$defs/table_cell" }
          }
        },
        "column_settings": {
          "type": "array",
          "maxItems": 20,
          "items": { "$ref": "#/$defs/table_column_setting" }
        }
      }
    },

    "task_card_block": {
      "description": "Standalone task_card block (also embeddable inline within plan_block).",
      "type": "object",
      "additionalProperties": false,
      "required": ["type", "task_id", "title"],
      "properties": {
        "type": { "const": "task_card" },
        "task_id": { "type": "string", "minLength": 1 },
        "title": { "type": "string", "minLength": 1 },
        "details": { "$ref": "#/$defs/rich_text_block" },
        "output": { "$ref": "#/$defs/rich_text_block" },
        "sources": {
          "type": "array",
          "items": { "$ref": "#/$defs/url_source_element" }
        },
        "status": { "enum": ["pending", "in_progress", "complete", "error"] },
        "block_id": { "$ref": "#/$defs/block_id" }
      }
    },

    "video_block": {
      "description": "Requires links.embed:write OAuth scope. video_url must be in app's unfurl domains, HTTPS, embeddable, return 2xx, not point to Slack-related domains.",
      "type": "object",
      "additionalProperties": false,
      "required": ["type", "alt_text", "title", "thumbnail_url", "video_url"],
      "properties": {
        "type": { "const": "video" },
        "alt_text": { "type": "string", "minLength": 1 },
        "title": {
          "allOf": [{ "$ref": "#/$defs/plain_text_object" }, { "properties": { "text": { "maxLength": 199 } } }]
        },
        "thumbnail_url": { "type": "string", "format": "uri" },
        "video_url": {
          "type": "string",
          "format": "uri",
          "pattern": "^https://"
        },
        "author_name": { "type": "string", "maxLength": 49 },
        "description": {
          "allOf": [{ "$ref": "#/$defs/plain_text_object" }, { "properties": { "text": { "maxLength": 199 } } }]
        },
        "provider_icon_url": { "type": "string", "format": "uri" },
        "provider_name": { "type": "string", "minLength": 1 },
        "title_url": {
          "type": "string",
          "format": "uri",
          "pattern": "^https://"
        },
        "block_id": { "$ref": "#/$defs/block_id" }
      }
    },

    "block": {
      "description": "Discriminated union of every Block Kit block type.",
      "oneOf": [
        { "$ref": "#/$defs/actions_block" },
        { "$ref": "#/$defs/alert_block" },
        { "$ref": "#/$defs/card_block" },
        { "$ref": "#/$defs/carousel_block" },
        { "$ref": "#/$defs/container_block" },
        { "$ref": "#/$defs/context_actions_block" },
        { "$ref": "#/$defs/context_block" },
        { "$ref": "#/$defs/data_table_block" },
        { "$ref": "#/$defs/data_visualization_block" },
        { "$ref": "#/$defs/divider_block" },
        { "$ref": "#/$defs/file_block" },
        { "$ref": "#/$defs/header_block" },
        { "$ref": "#/$defs/image_block" },
        { "$ref": "#/$defs/input_block" },
        { "$ref": "#/$defs/markdown_block" },
        { "$ref": "#/$defs/plan_block" },
        { "$ref": "#/$defs/rich_text_block" },
        { "$ref": "#/$defs/section_block" },
        { "$ref": "#/$defs/table_block" },
        { "$ref": "#/$defs/task_card_block" },
        { "$ref": "#/$defs/video_block" }
      ]
    },

    "modal_view": {
      "description": "Modal view surface (views.open / views.push / views.update payload). title/submit/close text capped at 24 chars. When blocks contain any input block, submit is required (per docs).",
      "type": "object",
      "additionalProperties": false,
      "required": ["type", "title", "blocks"],
      "properties": {
        "type": { "const": "modal" },
        "title": {
          "allOf": [{ "$ref": "#/$defs/plain_text_object" }, { "properties": { "text": { "maxLength": 24 } } }]
        },
        "blocks": {
          "type": "array",
          "minItems": 1,
          "maxItems": 100,
          "items": { "$ref": "#/$defs/block" }
        },
        "close": {
          "allOf": [{ "$ref": "#/$defs/plain_text_object" }, { "properties": { "text": { "maxLength": 24 } } }]
        },
        "submit": {
          "allOf": [{ "$ref": "#/$defs/plain_text_object" }, { "properties": { "text": { "maxLength": 24 } } }]
        },
        "private_metadata": { "type": "string", "maxLength": 3000 },
        "callback_id": { "type": "string", "maxLength": 255 },
        "clear_on_close": { "type": "boolean" },
        "notify_on_close": { "type": "boolean" },
        "external_id": { "type": "string", "maxLength": 255 },
        "submit_disabled": { "type": "boolean" }
      },
      "allOf": [
        {
          "if": {
            "properties": {
              "blocks": {
                "contains": {
                  "type": "object",
                  "properties": { "type": { "const": "input" } },
                  "required": ["type"]
                }
              }
            }
          },
          "then": { "required": ["submit"] }
        }
      ]
    },

    "home_view": {
      "description": "Home tab view surface (views.publish payload).",
      "type": "object",
      "additionalProperties": false,
      "required": ["type", "blocks"],
      "properties": {
        "type": { "const": "home" },
        "blocks": {
          "type": "array",
          "minItems": 1,
          "maxItems": 100,
          "items": { "$ref": "#/$defs/block" }
        },
        "private_metadata": { "type": "string", "maxLength": 3000 },
        "callback_id": { "type": "string", "maxLength": 255 },
        "external_id": { "type": "string", "maxLength": 255 }
      }
    }
  }
}